Silicon wafers are chemically etched to form semiconductor circuits. As part of the etching process a chemical typically referred to as photoresist is uniformly applied to the surface of the silicon wafer. A mask is then interposed between the silicon wafer and an energy source such as a light projector. The energy source is applied through the mask and exposes the photoresist. The photoresist is then dissolved with developers, leaving a pattern which is used to etch an image upon the silicon wafer.
Typically, photoresist is applied to the silicon wafer through a nozzle located at the center of the wafer. The wafer is rotated and centrifugal force distributes the photoresist along the surface of the wafer. Photoresist is expensive and it is therefore desirable to avoid applying more photoresist to a wafer surface than is required to properly coat the surface.
The present invention may improve the efficiency of coating a silicon wafer with a fluid. In one embodiment, the fluid is applied at the center of the silicon wafer and at a point between the center of the silicon wafer and the silicon wafer""s edge. In another embodiment, the progress of the fluid across the rotating wafer is monitored. The flow of the fluid is controlled such that excess fluid is not applied to the wafer. In yet another embodiment a first fluid application nozzle is located at the center of the silicon wafer. A second fluid application nozzle is interposed between the first application nozzle and the edge of the silicon wafer. A fluid is applied at the first nozzle and the wafer is rotated. As the photoresist progresses towards the edge of the silicon wafer, a sensor monitors the fluid progress and when the fluid reaches a predetermined point or radius, the flow of the fluid from the first nozzle is changed and the fluid is then dispensed through the second nozzle.
Another embodiment involves a method of applying fluid to a silicon wafer surface. A receiving surface is rotated about an axis. The receiving surface has an edge remote from the axis. A fluid is dispensed from a first nozzle onto the receiving surface at the axis from a first nozzle. Fluid is also dispensed onto the receiving surface from a second nozzle interposed between the first nozzle and the edge of the receiving surface.
Another embodiment involves an apparatus for uniformly coating a silicon wafer surface. A receiving surface is rotated about an axis. A first nozzle is positioned over the receiving surface proximate the axis. A second nozzle is over the receiving surface remote from the first nozzle.
In another embodiment, a method is disclosed for applying a fluid to a silicon wafer surface by rotating a receiving surface about an axis and dispensing a fluid onto a receiving surface proximate the axis. An energy stream is projected against the receiving surface. The energy reflected from the receiving surface is monitored to gather information about the receiving surface. The gathered information is used to then control the flow of the fluid to the receiving surface.
Another embodiment involves an apparatus for applying fluid to a silicon wafer surface. A receiving surface is rotatable about an axis. A nozzle is positioned over the receiving surface near the axis. An emitter projects an energy stream against the receiving surface. A receiver monitors the portion of the energy stream reflected from the receiving surface. A controller is in communication with the receiver. A conduit is in a fluid communication with the nozzle. A meter is disposed in the conduit. The meter is in communication with the controller and the meter is adapted to control the flow of the fluid through the conduit to the nozzle.
Another embodiment involves a method for applying fluid to a silicon wafer. A receiving surface is rotated about an axis. A fluid is dispensed from a first nozzle over the receiving surface proximate the axis onto the receiving surface. The outward flow of the fluid along the receiving surface is monitored and a fluid is dispensed from a second nozzle onto the receiving surface when the outward fluid flow reaches a predetermined radius from the axis.
In another embodiment, an apparatus for applying a fluid to a silicon wafer includes a receiving surface rotatable about an axis. The receiving surface has an exterior edge. A first conduit has a discharge orifice over the receiving surface near the receiving surface axis. The second conduit has a discharge orifice over the receiving surface between the axis and the exterior edge of the receiving surface. A first meter is adapted to control the flow of a fluid through the first conduit. A second meter is adapted to control the flow of the fluid through the second conduit. A monitor is adapted to detect the outward flow of the fluid along the receiving surface. A controller is in communication with the monitor and the meters and is adapted to control the meters.
In another embodiment a receiving surface is rotated about an axis and a fluid is dispensed onto the receiving surface at a first radius from the axis. The outward flow of the fluid is monitored and the fluid is dispensed from a second radius from the axis when the fluid dispensed at the first radius flows to a predetermined radius.
In yet another embodiment a method for coating a silicon wafer surface involves rotating a receiving surface about an axis. A fluid is dispensed onto the receiving surface at a first radius from the axis. The fluid is sensed at a second radius from the first axis. The flow of the fluid onto the receiving surface at the first radius from the axis is altered and the fluid is dispensed onto the receiving surface near the second radius.